Vermetid Buildups from Grand Cayman, British West Indies

Brian Jones, Ian G. Hunter

Abstract

Vermetid buildups, formed primarily of Dendropoma, are found in the coastal areas near Bodden Town and Great Bluff Estates on Grand Cayman. These gastropods are commonly encrusted by foraminifera (Homotrema rubum, Acervulina? sp.), coralline algae, and cyanobacteria. Spaces between the gastropods are filled with silt- to sand-sized sediment derived from the nearby lagoon. Bioerosion by echinoids, bivalves, worms, algae, and fungi substantially modified these buildups. C14 dating of the gastropod shells suggests that the in situ buildups died during the period of 1625-1740 AD. The presence of vermetids at these localities on Grand Cayman is not consistent with the high-energy conditions in which these gastropods usually thrive. Today, there are no living vermetids at these localities and the active biological processes are bioerosion and encrustation. The demise of the in situ vermetid buildups during the period of 1625-1750 AD may have been related to changes triggered by the Little Ice Age. Alternatively, their demise may have been caused by a change in sea-level or a significant reduction in the wave energy that was impinging on the coastlines.